1. Field of Invention
The present invention generally relates to control of viewing parameters for an image screen. More particularly, the invention relates to viewing parameter control for a portable computer image screen.
2. Description of Related Art
Effective and easy user control of viewing parameters, such as contrast, for a portable computer image screen is a problem. Previous solutions include a mechanically actuated thumb-wheel (e.g., the PalmPilo™ portable computer and the Palm III™ portable computer) and a mechanically actuated linear “slider” for contrast control. These actuators use mechanical potentiometers to adjust the screen contrast. One disadvantage of the mechanically actuated thumb-wheel solution as used for small, portable devices, such as the Palm III, has been that accidental adjustment of contrast occurs frequently because of contact between the thumb wheel and pockets and/or carrying cases.
The mechanical approaches are also typically complex, have relatively high failure rates and require special manufacturing operations (e.g., hand soldering).
U.S. Pat. No. 5,703,661, issued to Wu on Dec. 30, 1997 describes a device with contrast control. The '661 device provides an on-screen adjustment bar that indicates the status of the adjustment. But, the '661 control apparatus still uses a rotary input signal processor to make the actual adjustment, and therefore does not solve the accidental adjustment problem for portable computers.
None of the prior art apparatus and methods provides contrast control in a portable computer that solves the problem of inadvertant adjustment of the contrast while transporting the portable computer.